Spacers for Redistributing Forces for the Patella

ABSTRACT

Implant apparatus and methods directed toward treating conditions involving the knee joint and the patella specifically are disclosed. Full range of motion of the knee joint and tissue integrity are maintained in treatment approaches involving implanting a joint surface load reducing implant proximate the joint to change the direction of the tendons or muscles exerting forces on the joints.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application claims the benefit of U.S. Provisional Application No.61/568,615 filed Dec. 8, 2011, which is entirely incorporated herein byreference.

BACKGROUND OF THE DISCLOSURE

The present disclosure is directed towards systems and methods fortreating tissue of a body and more particularly, towards approachesdesigned to treat a natural joint and conditions involving the patellaspecifically.

A joint is the location at which two or more bones make contact. Theyare constructed to allow movement and provide mechanical support, andare classified structurally and functionally. Structural classificationis determined by how the bones connected to each other, while functionalclassification is determined by the degree of movement between thearticulating bones. In practice, there is significant overlap betweenthe two types of classifications.

There are three structural classifications of joints, namely fibrous orimmovable joints, cartilaginous joints and synovial joints.Fibrous/Immovable bones are connected by dense connective tissue,consisting mainly of collagen. The fibrous joints are further dividedinto three types: sutures which are found between bones of the skull;syndesmosis which are found between long bones of the body; andgomphosis which is a joint between the root of a tooth and the socketsin the maxilla or mandible.

Cartilaginous bones are connected entirely by cartilage (also known as“synchondroses”). Cartilaginous joints allow more movement between bonesthan a fibrous joint but less than the highly mobile synovial joint.Synovial joints have a space between the articulating bones for synovialfluid. This classification contains joints that are the most mobile ofthe three, and includes the knee and shoulder. These are furtherclassified into ball and socket joints, condyloid joints, saddle joints,hinge joints, pivot joints, and gliding joints.

Joints can also be classified functionally, by the degree of mobilitythey allow. Synarthrosis joints permit little or no mobility. They canbe categorized by how the two bones are joined together. That is,synchrondoses are joints where the two bones are connected by a piece ofcartilage. Synostoses are where two bones that are initially separatedeventually fuse together as a child approaches adulthood. By contrast,amphiarthrosis joints permit slight mobility. The two bone surfaces atthe joint are both covered in hyaline cartilage and joined by strands offibrocartilage. Most amphiarthrosis joints are cartilaginous.

Finally, diarthrosis joints permit a variety of movements (e.g. flexion,adduction, and pronation). Only synovial joints are diarthrodial andthey can be divided into six classes: 1. ball and socket—such as theshoulder or the hip and femur; 2. Hinge—such as the elbow; 3. Pivot—suchas the radius and ulna; 4. condyloidal (or ellipsoidal)—such as thewrist between radius and carps, or knee; 5. Saddle—such as the jointbetween carpal thumbs and metacarpals; and 6. Gliding—such as betweenthe carpals.

Synovial joints (or diarthroses, or diarthroidal joints) are the mostcommon and most movable type of joints in the body. As with all otherjoints in the body, synovial joints achieve movement at the point ofcontact of the articulating bones. Structural and functional differencesdistinguish the synovial joints from the two other types of joints inthe body, with the main structural difference being the existence of acavity between the articulating bones and the occupation of a fluid inthat cavity which aids movement. The whole of a diarthrosis is containedby a ligamentous sac, the joint capsule or articular capsule. Thesurfaces of the two bones at the joint are covered in cartilage. Thethickness of the cartilage varies with each joint, and sometimes may beof uneven thickness. Articular cartilage is multi-layered. A thinsuperficial layer provides a smooth surface for the two bones to slideagainst each other. Of all the layers, it has the highest concentrationof collagen and the lowest concentration of proteoglycans, making itvery resistant to shear stresses. Deeper than that is an intermediatelayer, which is mechanically designed to absorb shocks and distributethe load efficiently. The deepest layer is highly calcified, and anchorsthe articular cartilage to the bone. In joints where the two surfaces donot fit snugly together, a meniscus or multiple folds of fibro-cartilagewithin the joint correct the fit, ensuring stability and the optimaldistribution of load forces. The synovium is a membrane that covers allthe non-cartilaginous surfaces within the joint capsule. It secretessynovial fluid into the joint, which nourishes and lubricates thearticular cartilage. The synovium is separated from the capsule by alayer of cellular tissue that contains blood vessels and nerves.

Various maladies can affect the joints, one of which is arthritis.Arthritis is a group of conditions where there is damage caused to thejoints of the body. Arthritis is the leading cause of disability inpeople over the age of 65.

There are many forms of arthritis, each of which has a different cause.Rheumatoid arthritis and psoriatic arthritis are autoimmune diseases inwhich the body is attacking itself. Septic arthritis is caused by jointinfection. Gouty arthritis is caused by deposition of uric acid crystalsin the joint that results in subsequent inflammation. The most commonform of arthritis, osteoarthritis is also known as degenerative jointdisease and occurs following trauma to the joint, following an infectionof the joint or simply as a result of aging.

Unfortunately, all arthritides feature pain. Patterns of pain differamong the arthritides and the location. Rheumatoid arthritis isgenerally worse in the morning; in the early stages, patients often donot have symptoms following their morning shower.

Maladies that can affect the knee joint specifically include patellar orkneecap pain, misalignment or dislocation. Pain can exist when there isan excess of force contact between the patella and femur. This can bedue to misalignment associated arthritis or anatomical conditionsspecific to an individual. Kneecap dislocation occurs when thetriangle-shaped patellar bone covering the knee moves or slides out ofplace. This problem usually occurs toward the outside of the leg and canbe the result of patella misalignment due to patient specific anatomy orosteoarthritis, or from trauma.

The patella rests in the patellofemoral groove, a cavity located on theknee between the distal femur and the tibia. The sides of the patellaattach to certain ligaments and tendons to stabilize and support it. Theupper border of the patella attaches to the common tendon of thequadriceps muscles. The side or medial borders of the patella areattached to the vastus medialis muscle, and the lower border of thepatella is connected by the patellar ligament to the tibial tuberosity.The main ligament stabilizer, the patellofemoral ligament, restsdirectly over the femur and the patella while the lateral and medialcollateral ligaments acts as the secondary ligament stabilizers fromeither side of the patella.

Arthritis of the patella is one of the many causes of knee pain. Patellafemoral arthritis, is identified when loss of cartilage behind thepatella leads to pain in the knee. The pain typically worsens when apatient walks hills, goes up or down stairs, or does deep knee flexion.Arthritis of the patella can result from an injury to the knee joint,ordinary wear and tear, or most commonly the improper tracking of thepatella on the femur when the patella does not line up properly.

Non-surgical treatments for patella femoral arthritis include exercises,anti-inflammatory drugs, weight loss, pain medication and cortisoneshots to help lessen the pain. External braces or taping to improvepatella tracking can also be used. However, if sufficient bone lossoccurs, surgery may be necessary.

Surgical options include cartilage shaving, cartilage excision, drillinginto subchondral bone to induce regeneration or a lateral release wherea tendon is cut to help align the knee. Other surgical options include atibial tuberosity osteotomy, partial knee replacement and a total kneereplacement, or removal of the patella entirely.

In a tibia tuberosity osteotomy, the bump on which your patellar tendonattaches (tibial tuberosity) is moved surgically by cutting the bone andadding plates and/or pins. The tibial tuberosity is moved up, down, leftor right depending on the location of the damaged cartilage to move theload on the cartilage to a part of the knee that is stillhealthy—assuming there is such an area.

In a patellectomy the patella is removed outright. Sometimes this works,but sometimes removing the patella may hasten the onset of arthritis inthe rest of the knee. A patella replacement may also be performed wherepart or all of the patella is replaced with an implant.

Recently, less conventional approaches to treating the patella have beenproposed. In one approach, a patellar implant is placed below a patellartendon to elevate or tilt the patellar tendon. This consequently mayalter patellar tracking and decrease forces on the patella to therebyalleviate pain caused by the patella contacting the femur or tibia or bydecreasing force loads across the patella-femoral joint.

In a related approach, improper force distributions associated with thepatella are addressed by displacing tissues in order to realign forcevectors and alter movement across loading the knee joint. Here, again,an objective is to lessen the force with which the patella is pressedagainst the femur during the gait cycle.

Sufficient attention does not appear to have been given in prior patellatreatment approaches, however, to treatment of the knee joint throughoutits full range of motion. There is also a need for avoiding negativeremodeling of the patellar ligament as well as approaches to maintain adesired alignment of an implant and target tissue.

Therefore, what is needed and heretofore lacking in prior attempts totreat joint pain associated with patella misalignment or dislocation isan implantation method and implant device which addresses full range ofjoint movement, and which maintains desired structural integrity ofanatomy forming the knee joint.

The present disclosure addresses these and other needs.

SUMMARY

Briefly and in general terms, the present disclosure is directed towardstreating joint structures. In one aspect, there are disclosed approachesto redistributing forces of the patella to alleviate pain or to addressmisalignment.

In one particular embodiment, there is provided an implant which iscontoured to receive the patellar tendon. The contour of the implant isconfigured to define structure preventing the patellar tendon fromdisengaging from the implant during a full range of motion of a kneejoint. The implant is also contoured to avoid negative remodeling of thetissue of the knee.

In one embodiment, an implant for decreasing pain caused by misalignmentof bones at a joint includes an implant body configured to be implantedbeneath a tendon. The implant has a smooth upper surface for allowing atendon to slide over the implant body during articulation of the jointand a hook shaped portion configured to receive at least a portion ofthe tendon within an overhang of the hook to alter the tracking of thebones of the joint and alleviate pain associated with misalignment ofthe bones of the joint.

In one embodiment of a method for treating a knee joint suffering frompain, the method includes the steps of inserting an implant below apatellar tendon; and configuring the implant so that it engages thepatellar tendon throughout a full range of motion of the knee joint andso as to cause tension redistribution and contact force manipulation toalleviate pain.

In another embodiment of a method for treating a knee joint sufferingfrom pain, the method includes the steps of inserting an implant below aquadriceps muscle or quadriceps tendon; fixing the implant to the femur;configuring the implant so that it engages the quadriceps muscle orquadriceps tendon throughout a range of motion of the knee joint; andreducing compressive loads between the patella and femur with theimplant.

In another embodiment of a method for decreasing a force applied betweentwo bones of a joint, the method includes the steps of affixing animplant to a tendon at a location between the tendon and a bone at alocation proximate a the joint; allowing movement of the tendon andimplant over the bone during articulation of the joint; and decreasingcompressive loads between the two bones of the joint with the implant.

The implant can embody a fluid filled bladder which self-contours totissues. In one aspect, the implant can be adjustable through themovement, addition or removal of fluid. Various embodiments arecontemplated to treat patellar misalignment and to inhibit dislocation,as well as to absorb loads applied by the patella upon adjacent anatomy.

In a specific approach, an implant can include a two stage bladderhaving a main chamber for positioning under a ligament and a secondarychamber in communication with the main chamber. A valve can further beprovided between the main and secondary chambers. During gait, fluidremains in the main chamber and performs ligament tensioning. Duringrest periods and when the limb is straight, fluid passes to thesecondary chamber relieving tension on the ligament. This preventsnegative remodeling or stretching of the ligament, as the same causessuch therapy to become less effective over time.

An implant can include a chamber that is fluid or gas filled to providea compliant bolster and lengthening effect to increase a moment arm ofthe bolstered tendon or muscle. The chamber and bladder can be inflatedor expanded over time to provide an increasing size or stiffnessstructure, or deflated or contracted to provide an opposite effect. Avalve or injection port can be utilized for this functionality.

The implant can further be configured such that when a leg is inextension, there is no force or little force in a first chamber of theimplant. An elasticity of a second chamber is selected to cause fluid toflow into the first chamber. During gait, a valve between the chambersretains fluid within the first chamber. When at rest, with the joint inflexion the patella tendon presses fluid from the first chamber into thesecond chamber.

In yet another approach, an implant is provided to treat a joint andfunctions to redistribute forces of a patella. The implant includesstructure accomplishing attachment of the implant to the patella tendon.This implant can be a single spacer or can include one or more chambersthat contain fluid or gas. Such an implant thus remains in place duringa full range of motion of a knee joint.

Other features and advantages of the present disclosure will becomeapparent from the following detailed description, taken in conjunctionwith the accompanying drawings, which illustrate, by way of example, theprinciples of the disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front view, depicting an implant attached to membersdefining a joint according to an embodiment of the present disclosure;

FIG. 2 is a cross-sectional view, depicting the structure of FIG. 1taken along line 2-2;

FIG. 3 is a perspective view, depicting the implant of FIG. 1;

FIGS. 4A and 4B are side views, depicting a knee joint with and withouttibial and femur implants;

FIGS. 5A and 5B are side views, depicting the knee joint and implants ofFIGS. 4A and 4B with the joint flexed to about 30 degrees;

FIGS. 6A and 6B are side views, depicting the knee joint and implants ofFIGS. 4A and 4B with the joint flexed to about 75 degrees;

FIGS. 7A, 7B and 7C are front views, depicting implants attached tomembers of a joint with a tibial implant only, a femoral implant onlyand both tibial and femoral implants according to an alternative exampleembodiments of the present disclosure;

FIGS. 8A-8E are front views, depicting implants having different shapesattached to a bone of a joint according to an alternative exampleembodiments of the present disclosure;

FIGS. 9A-9D are top views of implants having different shapes accordingto alternative embodiments of the present disclosure;

FIGS. 10A-10C are top views of implants having different inclinations ofthe superior surface according to alternative embodiments of the presentdisclosure;

FIGS. 11A-11C are top views of implants having different heights anddifferent shapes according to alternative embodiments of the presentdisclosure;

FIGS. 12A and 12B are side views, depicting the knee joint and implantshaving different extensions with respect to the joint surfaces of FIGS.8B and 8C;

FIG. 13 is a front view, depicting an implant attached to membersdefining a joint according to alternative example embodiment of thepresent disclosure;

FIG. 14 is a cross-sectional view, depicting the structure of FIG. 1taken along lines 5-5;

FIG. 15 is yet another front view, depicting an implant attached tomembers defining a joint according to alternative embodiments of thepresent disclosure;

FIG. 16 is a cross-sectional view, depicting the structure of FIG. 1taken along lines 7-7;

FIG. 17 is a front perspective view depicting an implant with a rolleraccording to an alternative embodiment of the present disclosure;

FIG. 18 is a side cross-sectional view of the implant of FIG. 17 withthe knee joint at full extension;

FIG. 19 is a side cross-sectional view of the implant of FIG. 17 withthe knee joint in flexion;

FIG. 20 is cross-sectional view of the implant of FIG. 17 taken along anaxis of the roller;

FIG. 21 is a side view, depicting an implant according to alternativeembodiments of the present disclosure;

FIGS. 22 and 23 are perspective views, depicting the implant of FIG. 21;

FIG. 24 is a front view, depicting an implant placed at a jointaccording to an alternative embodiment of the present disclosure;

FIG. 25 is a front view, depicting a an implant placed at a jointaccording to an alternative embodiment of the present disclosure; and

FIG. 26 is a cross-sectional view of an implant according to analternative embodiment of the present disclosure.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the drawings, which are provided by way of example andnot limitation, the present disclosure is directed towards apparatus andmethods for treating a joint, and in particular, for treating a kneejoint and for relieving pain caused by conditions involving the patella.Patella femoral osteoarthritis can be due to natural anatomymisalignment or can be a function of an earlier injury. Significant paincan be associated with these patellar conditions and can be a directresult of excessive forces being generated between the patella andadjacent anatomy. In particular, pain results when there are undesirableforce contacts between the patella and the femur. The present disclosureis directed at alleviating pain by redirecting or absorbing excessforces without permanently remodeling tissues critical to thefunctioning of the knee joint.

As shown in FIGS. 1-3, one approach to treating conditions involving apatella 90 can include the placement of an implant 100 at the knee joint102. The implant 100 can be generally U-shaped and can include terminalends 104 configured to be affixed to body anatomy. In one approach, theterminal ends 104 include through holes 106 sized and shaped to receivebone screws 108 or other affixation structure. In this way, the implant100 can be attached directly to tibia 112 of the knee joint 102.Although the implant 100 is shown attached to the tibia 112, it can alsobe affixed to the femur 110 as will be discussed further below.

Although the present apparatus and method are described particularly forreducing pain of patellar chondromalacia or osteoarthritis due todamaged cartilage on the surfaces of the patella and the trochleargroove of the femur, embodiments of the disclosure can be used torelieve the loads on other joints in a similar manner. By changing thedirection and position of tendons and muscles that exert forces onjoints, the implants function as a tissue elevator to reduce compressiveloads on joint surfaces.

As shown in FIG. 1, the implant 100 is affixed to the tibia 112 suchthat a midsection 120 of the implant 100 is configured under thepatellar tendon 130. The terminal ends 104 of the implant 100 are showndirected away from the knee joint 102 but can alternatively be pointingtoward the knee joint 102 or wrapping around the tibia 112.

The implant 100 is further contoured to define a low profile attachmentstructure. It is thus contemplated that a lower surface 140 of theimplant 100 be curved to mimic the shape of the structure to which theimplant engages, such as the tibia 112, or femur 110. An upper surface142 is also contoured so as to fit nicely with the knee anatomy and mayinclude a lubricious coating or material permitting relative motionbetween the implant and knee anatomy. The implant 100 may be provided indifferent sizes having different heights of the midsection 120 to allowa selection of different patellar tendon force reduction heights.

Once an implant 100 of a selected height is inserted beneath thepatellar tendon 130 the effective angle of action of the patellar tendonon the patella 90 is modified reducing the force with which the patellartendon presses the patella against the femur.

The upper surface 142 of the implant 100, as shown in FIG. 2, furtherincludes a recess 144 designed to receive the patellar tendon 130. Therecess 144 defines a trough through which the patella tendon 130 can betranslated throughout a full range of articulation and valgus and varusmotion or other rotation or movement of the knee joint. Thus, a portionof the patellar tendon 130 remains within the recess 144 throughout gaitas well as when the knee joint 102 is in complete flexion or extension,and all angles therebetween, and when the knee joint is loaded andunloaded. Without the recess 144 or other structure for guiding thetendon over the implant 100, the tendon can slide off of the implantduring a portion of the motion of the joint. In addition to guiding thetendon 130 over the implant 100 in the ordinary natural path of thetendon, the implant may also be arranged to alter the path of the tendonand thereby correct improper tracking of the patella over the femur. Forexample, where the patella 90 is shifted medially and this shift iscausing wear and associated pain in the joint, the implant 100 can shiftthe patellar tendon laterally to reorient the tracking of the patellawhile also reducing the load on the patella by changing the angle ofaction of the patellar tendon. In the case of redirecting the trajectoryof the patellar tendon, the recess 144 in the implant 100 can bemodified to have more pronounced edges to achieve this redirection.

FIGS. 4A and 4B illustrate a joint at extension with and without atibial implant 100 and a femoral implant 600 secured to the tibia andfemur with bone screws (not shown). The position of the tibial implant100 beneath the patellar tendon 130 and the femoral implant 600 beneaththe quadriceps muscle or quadriceps tendon 132 reduces the load on thepatellar/femoral surfaces, thus reducing patellar/femoral pain. Thereduction in contact between the patellar and femoral joint surfaces canbe seen by comparison of FIG. 4A without implants to FIG. 4B withimplants. The magnitude of reduction in contact is dependent on theimplant height selected. A large implant height is shown in FIG. 4B byway of example to more clearly show the reduction in contact forces. Thepatella 90 need not be lifted entirely off the patella when the knee isat full extension to provide pain relief.

FIGS. 5A and 5B illustrate the reduction in load between the patella 90and the femur 110 at about 30 degrees of flexion of the joint. As can beseen in FIG. 5B, the distal portion of the patella 90 is lifted awayfrom the femur 110, significantly reducing load at this portion of thejoint at partial flexion.

FIGS. 6A and 6B illustrate the reduction in load between the patella 90and the femur 110 at about 75 degrees of flexion of the joint. As can beseen in FIG. 6B, the proximal portion of the patella 90 is lifted awayfrom the femur 110, however the amount of load reduction my be tailoredto the particular application by altering the configuration of theimplants.

The patellar implants 100, 600 can be configured to include one or morestructures that only applies tension during gait, and then, during onlyportions of the gait cycle. Such structure can also include a loadabsorption component acting during such intervals. Through thisapproach, undesirable permanent remodeling of knee structure, and inparticular unwanted lengthening of the patellar tendon, can be avoided.One way to achieve intermittent activation of the implant is to have amulti-compartment expandable implant which inflates and deflates basedon joint action. These inflatable implants will be described in furtherdetail below.

Referring now to FIGS. 7A-7C, the tibial implant 100 and femoral implant600 can be used either alone or in combination. The implants of FIGS.7A-7C have a C-shaped design that wraps around the bone shaft between 45and 180 degrees of the circumference of the bone. The wrapping around ofthe C-shaped design allows several muscles and/or tendons to beredirected or repositioned by the implant.

FIG. 8A illustrates an I-shaped implant 610 configured to be attached tothe femur 110. At the position shown in FIG. 8A the implant 610 wouldreside partly beneath the patella (not shown) when the knee joint is atfull extension. The I-shaped implant sits at the end of the femur 110near the joint and elevates the quadriceps muscle and tendon.

FIGS. 8B and 8C illustrate two variations of an I-shaped implant for thetibia. The wider implant 160 extends beyond the bone contact region andthe narrower implant 170 does not extend past this contact region. Theseimplants are shown in further detail in FIGS. 12A and 12B. FIGS. 8D and8E illustrate J-shaped implants 180, 190 which have a single legextending along the bone shaft for improved bone attachment. Thesedifferent designs with different attachment mechanisms can provide thesurgeon with options for attachment to bone with bone screw locationsthat avoid disruption to the ligaments, muscles and subchondral regionsof the bone.

FIGS. 9A-9D illustrate different cross section profiles for the implantsincluding those having top surfaces which are flat, saddle shaped,convex, or concave. These profiles can apply to both tibial implants 100and femoral implants 600. The implant of FIG. 9A has a concave lowersurface 650 configured to correspond generally to the shape of the boneand a convex upper surface 652 configured to support the overlyingtendon or muscles. Medial and lateral flanges 654 at the edges of thetop surface help prevent the tendons or muscles from sliding off of theimplant. A plurality of feet 656 on the lower surface 650 are configuredto contact the bone and allow for the implant to accommodate differentanatomical variations between patients. At least one foot 656 andpreferably three feet extend from the implant on the bone-facing surfaceor bottom surface of the implant to make contact with the bone. The feetprovide an offset which allows the implant to be seated on the bonesurface despite slight variations in bone surface geometries betweenpatients and despite slight variations in positioning of the implant.The feet 656 can be provided on any of the embodiments of the implantsdescribed herein and will tightly contact the bone or the periosteumwhen the bone screws are tightened to press the implant against thebone.

FIG. 9B has a concave lower surface 660 and a substantially flat uppersurface 662 with lateral flanges 664. Each of the implants has two ormore holes for receiving bone screws. FIGS. 9C and 9D have varioussaddle shaped lower and upper surfaces with bone screws inserted fromthe proximal or distal side of the implant (FIG. 9C) and from the medialand lateral sides of the implant (FIG. 9D). The saddle top provides astabilizing effect to keep the tendons or muscles from sliding off ofthe top of the implant.

The flat top cross section of the implant 100 b of FIG. 10B produces aone directional displacement of a tendon or muscle providing primarilyunloading of the patella/femoral joint. The implant may also have anmedial/lateral inclination as shown in the implant 100 a of FIG. 10A toboth reduce the load on the joint and also to shift the load on thejoint medially or laterally. The implant 100 c of FIG. 10C has a partlyflat and partly angled surface which may both shift the load and reducethe load.

FIGS. 11A-11C show a series of implants of differing heights h. Implantshaving heights from 2 mm to 60 mm may be provided to allow the surgeonto select the implant that unloads the joint to the desired degree. FIG.11C illustrates an offset height f provided by the feet 656. The heightf of the feet is about 2-5 mm, preferably about 3 mm.

FIG. 12A further illustrates the tibial implant 160 which has anoverhang or projection 162 which extends by a distance X beyond a lineformed at the bone contacting surfaces. This overhang 162 increases theeffectiveness of the implant 160 at larger angles of flexion. Thefemoral implant 600 is also provided with an overhang 602, however theoverhang of the femoral implant does not extend beyond the joint contactsurfaces. The implant 170 of FIG. 12B shows no overhang, however theimplant is positioned close to or adjacent the joint contact surfaces.

Referring to FIGS. 13 and 14, there is shown another embodiment of animplant 200. As before, the implant can be generally U-shaped, C-shaped,I-shaped or J-shaped and includes terminal ends 204 configured to beaffixed to body anatomy. Again, through holes are provided to receiveaffixation structure such as bone screws 108 so that the implant can beattached directly to knee anatomy. A lower surface 240 of the implant200 be curved to mimic the shape of the structure to which the implant200 engages, such as the tibia 112 or femur 110. An upper surface 242 ofthe implant 200 is intended to be lubricous to permit relative movementwith a patellar tendon 130. Moreover, the implant 200 can be configuredwith its terminal ends 204 directed toward or away from the knee joint102 and can include a midsection with a recess 244 shaped to receive thepatellar tendon 130 through a full range of motion of the knee.

This embodiment of the implant further includes a fluid, gas or gelfilled chamber or bladder 250 which is accessible by an injection port252. The chamber 250 can form an integral structure with remainingportions of the implant 200 and portions of the implant 200 can embodyfiber woven reinforced fixation material to form a single bodiedstructure. The injection port 252 is employed to both place substanceswithin the chamber 200 and to be accessible to alter the volume orcomposition of the substance before and after implantation. Theinjection port 252 can also be used to remove all or most fluid whenimplanting or removing the implant 200 or to alter the softness orrigidity of the implant. The structure defining the chamber 250 can havean elasticity greater than that chosen for the remaining portions of theimplant 200, such as for example the terminal ends 204 which aredesigned to have a rigidity or robustness suited for permanentattachment to knee anatomy. The materials are of course chosen to bebiocompatible in any event.

The substance chosen to fill the chamber 250 is selected to cooperatewith the material chosen for walls defining the chamber 250 so thatdesired load redirection can be effectuated. It is further contemplatedto take advantage of fluid responses of the substances chosen forplacement within the chamber 250. For example, a viscous fluid or gelsuch as silicone hydrogel flows smoothly under low strain rates, butresists flow under high strain rates. Therefore, the fluid or gas chosenis intended to have a viscosity and the chamber walls are designed tohave a flexibility to redirect load to alleviate pain. Such loadredirection can be reserved to occur primarily gait, and for thatmatter, during only portions of gait with greater flexion angles. Duringjoint extension, or otherwise when there is less pain due to forcesassociated with the patella this manipulation is reduced so thatundesirable remodeling is avoided.

Thus, as the knee joint 102 articulates during gait, the patellar tendon130 is guided through the implant recess 244. The load redirectingchamber 250 is sized and shaped to span the recess 244 so that duringcertain portions of gait having medium to high flexion angles, a heightof the chamber 250 is at a maximum to provide maximum load redirectionand reduced load applied directly between the patella 90 and femur 110.For example, forces between the patella 90 and the femur 110 can bereduced and angles of action of the patellar tendon 130 can be modifiedto thereby minimize pain.

In yet another approach (FIGS. 15 and 16), the implant 300 can furtherinclude multiple chambers 350, 352 that are in fluid communication andwhich are versatile in accommodating tension and contact forces. Asbefore, a lower surface 340 of the implant 300 be curved to mimic theshape of the structure to which the implant 300 engages, such as thetibia 112 or femur 110. An upper surface 342 of the implant 300 isintended to be lubricous to permit relative movement with a patellartendon 130. Moreover, the implant 300 can be configured with itsterminal ends 304 directed toward or away from the knee joint 102 andcan include a midsection with a recess 344 shaped to receive thepatellar tendon 130 through a full range of motion of the knee.

The generally U-shaped device can be extended to provide a platformabout each of the chambers 350, 352. Here, again, the chambers 350, 352are designed to receive gases or fluids which embody desirable viscositycharacteristics. Additionally, the first chamber 350 is intended to bearranged to be in apposition with the patella tendon 130 and the secondchamber 352 is to be positioned remote from the tendon 130 in an areawhere the chamber will be free to fill and empty in a relativelyunobstructed manner. Also, as before, the walls defining the chambers350, 352 are formed from materials having an elasticity designed toachieve desired force reorientation throughout the full range of motionof the knee joint. An injection port 354 is additionally included toprovide access to the second chamber 352 so that the volume orcomposition of the substance in the chamber can be altered.

A neck 356 joining the first 350 and second 352 chambers provides thefluid communication between the structures. A valve (not shown) can beconfigured in this area or the neck 356 can define a small opening. Ineither approach, the neck 356 can be configured to play a role in themovement of fluid from one chamber to the next. For example, when a legof an individual is in extension, there is no force or little force onthe first chamber 350. The elasticity of the second chamber 352 ischosen to thus cause fluid to flow into the first chamber 350. Duringgait, the sizing of the neck 356 is such that its flow access is limitedso that there is insufficient time for fluid to pass from the firstchamber 350 to the second chamber 352. Rather, the fluid remains butflows within the first chamber 350 to thereby provide forcereorientation. When seated or otherwise placing the knee joint 102 inother resting or non-gait positions, with the joint in flexion, theforce of the patellar tendon 130 presses fluid out of the first chamber350 into the second chamber 352. As such, the first chamber 350 isreduced in size during this juncture, and the patellar tendon 130 is notsubjected to the increased tension caused by the implant 300. By notengaging in this manipulation, the patellar tendon 130 can be unloadedand remodeling thereof is avoided.

In another embodiment, the second chamber 352 can be positioned withinan anatomical structure, such as a muscle, and the fluid will be forcedinto the first chamber 350 by activation of the muscle. Therefore, theimplant 300 can be activated by muscle activation, such as duringrunning or walking, and can remain relatively passive at other times.

FIGS. 17-20 illustrate a further embodiment of an implant 700 having aroller 710. The implant 700 is designed to further reduce the frictionbetween the implant and the tissue sliding over it. The roller 710 makescontact with the tendons, muscles and other tissues to reduce potentialtissue irritation including tendonitis, inflammation, tendon tears andrupture. The roller 710 is supported in the implant 700 within blindbores 712 by bearing rollers 714. Bearing rollers 714 are protected by aseal 716 in the form of O-rings, quad rings, lip seals or the like.

In a related approach, as shown in FIGS. 21-23, an implant 400 designedto accomplish force reorientation can be affixed directly to thepatellar tendon 130. This implant 400 can further include one or more ofthe features described above including one or more fluid filledchambers. Further, it is again contemplated that the device be formedfrom biocompatible materials. This particular implant 400 furtherembodies a porous or mesh tendon contacting surface 402 and a lubriciousbearing surface 404 for sliding contact with bone. The porous meshsurface 402 supports ligament ingrowth and aids in attachment to thepatellar tendon 130. The lubricious bearing surface 404 slides alongknee anatomy during articulation. Through holes 406 are further providedand sized and shaped to receive fastening structures 410 for assuring astrong affixation to the patellar tendon 130. In this way, relativemovement between the implant 400 and ligament is eliminated and theimplant 400 is thus always correctly positioned to provide desired forcereorientation and pain relief. Other methods for attachment of theimplant 400 to the patellar tendon 130 or other tendons or muscles mayalso be used including known tissue ingrowth surfaces on the implant,sutures, mechanical clamping or combinations of attachment mechanisms.There is no risk of the patellar tendon remodeling around the implant400 because the implant is connected directly to the tendon.

With reference to FIG. 24, there is shown in yet another embodiment ofan implant 500. This implant 500 can include one or more of the abovedescribed features, such as one or more chambers, and further embodies agenerally inverted J-shape. A vertically extending portion 502 of theimplant 500 is provided with through holes sized and shaped to receivefastening structure such as bone screws 108. A laterally extendingportion 508 includes a recess 510 for receiving a patellar tendon 130.Although the implant 500 is shown attached to the tibia 112, it can alsobe affixed to the femur 110 as well. This approach illustrates that anasymmetric implant can be employed to accomplish desired treatment ofthe patella 90. A further deviation would be to eliminate the verticallyextending portion 502 and to include affixation structure within therecess 510. The implant 500 also has a trough or recess as in theimplant shown in FIG. 2 to guide in tracking the patellar tendon overthe implant in a desired trajectory.

FIG. 25 shows a hook shaped implant 500a which functions to both elevatethe tendon 130 and to alter the tracking of the patella 90. A hook 520can move the patellar tendon and consequently the patella itselflaterally, such as toward the lateral side of the knee when the patellapain is caused by improperly tracking to far to the medial side. Thehook 520 is sized to receive at least a portion the tendon underneaththe hooked portion of the implant.

FIG. 26 illustrates a bridge shaped implant 800 which lifts the patellartendon 130 in a manner similar to the lift implants shown herein, butlifts from the superior surface of the patellar tendon rather than fromthe inferior surface. The bridge can be attached to the patellar tendon130 by sutures, mechanically clamped, tissue ingrowth or a combinationthereof.

The various embodiments of the implants describe herein may be made froma wide range of materials. According to one embodiment, the implants aremade from metals, metal alloys, or ceramics such as, but not limited to,Titanium, stainless steel, Cobalt Chrome or combinations thereof.Alternatively, the implants are made from thermo-plastic materials suchas, but not limited to, high performance polyketones includingpolyetheretherketone (PEEK), ultra-high molecular weight polyethylene(UHMWPE), PyroCarbon or a combination of thermo-plastic and othermaterials. Various embodiments of the implants are relatively rigidstructures.

Conventional approaches to inserting the above-described implants withinknee anatomy are contemplated. Arthroscopic approaches can be employedalong with fluoroscopy or other imaging techniques to properly positionthe treatment devices. Prior to implantation, the anatomy of thepatient's knee is accessed to determine a best course of treatment, andto identify a configuration of implant which best suits the patient'sspecific condition. The knee is rotated and turned through its fullrange of motion to identify proper implantation sites and to access thebest manner for redistributing tensions and contact forces, with theobjective of reducing pain. Further, the implant is configured in itsmost compressed configuration for implantation and then reconfigured tofunction in a treatment capacity. Subsequent to implantation, theimplant can be reconfigured to present an altered profile to achieveoptimum results.

The foregoing therefore provides an implant embodying a compliantbolster and lengthening affect to increase a moment arm of the bolsteredpatellar tendon for the purpose of relieving pain or other symptomsinvolving the patella. The size or stiffness of the implant can bealtered to achieve the desired bolstering or manipulation of tension andcontact forces.

Thus, it will be apparent from the foregoing that, while particularforms of the apparatus and method have been illustrated and described,various modifications can be made without parting from the spirit andscope of the disclosure. In particular, one or more features of onespecific approach can be incorporated into another approach.Additionally, the present disclosure can be made to be applicable toother medical conditions.

We claim:
 1. A knee joint implant, comprising: a patellar tendonengaging portion, the patellar tendon engaging portion configured toengage a patellar tendon throughout a full range of motion of a kneejoint; and a tension redistribution and contact force manipulationportion configured to alleviate pain associated with patellamisalignment.
 2. The knee joint implant of claim 1, wherein the tensionredistribution and contact force manipulation portion is configured tooperate during less than an entire portion of a gait cycle.
 3. The kneejoint implant of claim 1, the patellar tendon engaging portion furthercomprising a first chamber containing a gas or fluid.
 4. The knee jointimplant of claim 3, wherein the first chamber contains a hydrogel. 5.The knee joint implant of claim 3, the patellar tendon engaging portionfurther comprising a second chamber configured to be in fluidcommunication with the first chamber.
 6. The knee joint implant of claim5, further comprising a neck structure joining the first chamber and thesecond chamber.
 7. The knee joint implant of claim 6, further comprisinga valve configured within the neck structure.
 8. The knee joint implantof claim 6, wherein the neck structure is configured to control movementbetween the first chamber and the second chamber.
 9. The knee jointimplant of claim 3, further comprising an injection port through whichthe gas or fluid can be passed into or out of the first chamber.
 10. Theknee joint implant of claim 5, further comprising an injection portthrough which the gas or fluid can be passed into or out of the firstchamber or the second chamber.
 11. The knee joint implant of claim 3,wherein the gas or fluid flows within the first chamber to provide arange of tension redistribution and contact force manipulation duringportions of a gait.
 12. The knee joint implant of claim 5, wherein thegas or fluid flows between the first chamber and the second chamber toprovide a range of tension redistribution and contact force manipulationduring portions of a gait.
 13. The knee joint implant of claim 5,wherein the gas or fluid passes to the second chamber during rest andwhen the patellar tendon is straightened to relieve tension on thepatellar tendon and to avoid remodeling of anatomy.
 14. The knee jointimplant of claim 1, wherein the implant is configured to avoid permanentremodeling of knee anatomy.
 15. The knee joint implant of claim 1,wherein a substance is employed as the gas or fluid so that there is asmooth flow of the substance under low strain rates, but flow isresisted under high strain rates.
 16. The knee joint implant of claim 1,wherein the implant defines a bolster and creates a patellar tendonlengthening effect to increase a moment arm of a bolstered patellatendon.
 17. The knee joint implant of claim 1, wherein the implant isgenerally U-shaped.
 18. The knee joint implant of claim 1, wherein theimplant is generally J-shaped.
 19. The knee joint implant of claim 1,further comprising one or more fasteners to attach the implant to kneeanatomy.
 20. The knee joint implant of claim 19, wherein the implant isattached to the patellar tendon so that relative motion between theimplant and the patellar tendon is eliminated.
 21. The knee jointimplant of claim 20, the patellar tendon engaging portion furthercomprises an upper side facing the patellar tendon that includes atissue ingrowth structure.
 22. The knee joint implant of claim 21, thepatellar tendon engaging portion further comprising a lower sideincluding a lubricious surface.
 23. The knee joint implant of claim 18,the patellar tendon engaging portion further comprising an upper surfacefacing the patellar tendon that includes a lubricious surface.
 24. Theknee joint implant of claim 18, the patellar tendon engaging portionfurther comprising an upper surface including a trough for receiving aportion of the patellar tendon throughout the full range of motion ofthe knee joint.
 25. A method for treating a knee joint suffering frompain, comprising: inserting an implant below a patellar tendon; andconfiguring the implant so that it engages the patellar tendonthroughout a full range of motion of the knee joint and so as to causetension redistribution and contact force manipulation to alleviate pain.26. The method of claim 25, wherein tension redistribution and controlforce manipulation operates less than an entire portion of a gait cycle.27. The method of claim 25, further comprising configuring the implantso that permanent remodeling of the patellar tendon is avoided.
 28. Themethod of claim 26, further comprising providing the implant with atleast one chamber containing a substance which flows within the at leastone chamber to accomplish desired tension and force manipulation. 29.The method of claim 25, wherein the implant is inserted in a compressedstate.
 30. The method of claim 28, further comprising providing theimplant with an injection port to insert or remove the substance fromthe chamber to thereby change the profile or rigidity of the chamber.31. An implant for decreasing pain caused by misalignment of bones at ajoint, the implant, comprising: an implant body configured to beimplanted beneath a tendon, the implant having a smooth upper surfacefor allowing a tendon to slide over the implant body during articulationof the joint and a hook shaped portion configured to receive at least aportion of the tendon within an overhang of the hook shaped portion toalter the tracking of the bones of the joint and alleviate painassociated with misalignment of the bones of the joint.
 32. The implantof claim 31, wherein the implant body has a bone contacting surface andthe hook shaped portion extends away from the bone contacting surface.33. The implant of claim 32, further comprising at least one throughhole and at least one bone screw received in the through hole forattaching the implant body to a bone.
 34. The implant of claim 33,wherein the bone contacting surface is a concave surface configured toreceive a curved bone surface.
 35. A method for treating a knee jointsuffering from pain, comprising: inserting an implant below a quadricepsmuscle or a quadriceps tendon; fixing the implant to the femur;configuring the implant so that it engages the quadriceps muscle or thequadriceps tendon throughout a range of motion of the knee joint; andreducing compressive loads between a patella and a femur with theimplant.
 36. A method of decreasing a force applied between two bones ofa joint, comprising: affixing an implant to a tendon at a locationbetween the tendon and a bone proximate to the joint; allowing movementof the tendon and implant over the bone during articulation of thejoint; and decreasing compressive loads between the two bones of thejoint with the implant.
 37. The method of claim 36, wherein the implantis a rigid implant.
 38. The method of claim 36, wherein the joint is aknee joint.